Impacts of size and cross-sectional shape on surface lattice constant and electron effective mass of silicon nanowires

We investigate the surface lattice and electronic structure of [110] oriented hydrogen-passivated silicon nanowires (SiNWs) of different cross-sectional shapes by using the first-principles tight-binding method. Remarkable quantum confinement effects are observed on the surface lattice constant and the electron effective mass. Moreover, with the same cross-sectional area, the triangular-SiNW has more obvious size dependence than rectangular-SiNW. The significant size and cross-sectional shape effects are explained by the concept of surface-to-volume ratio. Our results demonstrate that due to the smaller electron effective mass, the rectangular-SiNW has obvious advantage over triangular-SiNW in application in higher on current in SiNW transistor.